Search Results (15)

High-latitude regions store substantial amounts of soil organic matter (SOM). Icelandic volcanic soils have exceptional capabilities for SOM accumulation, but recent changes in land use can significantly impact it. Water-extractable organic matter (WEOM) represents a labile SOM pool and serves as a reliable index of SOM dynamics. We assessed the stable carbon (C), stable nitrogen (N), and WEOC (water-extractable organic carbon), as well as WETN (water-extractable total nitrogen), concentrations in soils under different land uses—semi-natural habitats (tundra and wetland) and human-managed areas (intensively and extensively grazed pasturelands and formerly and presently fertilized meadows)—in southeastern Iceland. The results suggest that human-managed sites contain more total C and N but less WEOM per unit of total C or N than semi-natural habitats, except for wetlands. Wetlands exhibited the highest WEOM content. Extensive pasturelands and fertilized meadows are becoming more common in local ecosystems, highlighting the direction of changes in Icelandic grasslands management. Full article

Soil health is typically evaluated using physical, chemical, and biological parameters. However, identifying cost-effective and interpretable metrics remains a challenge. The effectiveness of ecological outcome verification (EOV) in predicting soil health in grazing lands was assessed at 22 ranches. Sixty-four soil samples were analyzed using the Haney soil health test (HSHT) and phospholipid fatty acid (PLFA). Of 104 variables, 13 were retained following principal component analysis (PCA), including variables associated with plant community, carbon dynamics, and microbial community structure. Soils with enriched microbial and organic matter (SOM) characteristics supported a healthier ecological status, as corroborated by greater EOV scores. Water-extractable organic carbon (WEOC) was positively correlated to plant functional groups, whereas SOM was positively correlated with plant biodiversity and functional groups. Total bacteria were positively correlated with all EOV parameters. Microbial biomass (MB) was positively correlated with both water and energy cycle indexes, whereas arbuscular mycorrhizal fungi (AMF) was positively correlated with the water cycle. From the multiple regression analyses, water infiltration emerged as a key predictor of soil respiration and WEOC. Overall, the ecological outcomes measured by EOV have the potential to serve as a proxy for soil health, providing a practical tool for producers to make informed land management decisions. Full article

The present study highlights the possibility of using sewage sludge-derived compost (SSC) or biochar (SSB) as valuable organic amendments. Such utilization of sewage sludge fulfills the principles of a carbon farming and nature-based solution strategy (NBS). This study focused on a detailed analysis of quantitative and qualitative changes in soil C compounds (total carbon—TC, total organic carbon—TOC, humic substances—CHS, labile carbon—LC, and water extractable organic carbon—WEOC), which resulted from the application of SSC or SSB; an assessment of variability in total and available forms of N and S as biogenic components that are integrally related to the organic matter of the amendments used in the experiment; and an indication of the possible relationships between C compounds and available nutrients. The experiment was conducted under greenhouse conditions with terra rosa soil amended with SSC or SSB at different application rates (25, 50, 75, 100% by mass). Soil samples were analyzed for the abovementioned parameters using appropriate analytical methods. Regardless of the organic amendment, the values of tested parameters increased with the applied dose, with the differences being significantly greater in relation to the contents determined for the control soil. In general, the application of SSC was more favorable than SSB, which was manifested by 12–49-fold higher TOC, 6–24-fold higher total N, and 10–41-fold higher total S levels. An exception was found for the content of available sulfur, which was significantly higher in the soil fertilized with biochar. In addition, SSC contributed more humic acid carbon (12.5–24.15 g∙kg⁻¹) and labile carbon (10.34–27.37 g∙kg⁻¹). On the other hand, SSB had a greater effect on fulvic acid carbon levels (2.18–2.75 g∙kg⁻¹), which were comparable to the levels of LC (3.44–6.86 g∙kg⁻¹) and WEOC (2.56–6.28 g∙kg⁻¹). The research results highlighted the validity of processing SS into compost or biochar for further use for agricultural/reclamation purposes. Despite their different impacts on the studied soil properties, both organic amendments are important for maintaining soil health and can play a significant role in carbon farming as NBS practices. The findings allow us to conclude that the strategy of increasing the amount of C through SSC or SSB fertilization is the advisable direction in sustainable soil management. Full article

Continuous agricultural activities lead to soil organic carbon (SOC) depletion, and agroecological intensification practices (i.e., reduced soil disturbance and crop diversification) have been suggested as strategies to increase SOC storage. The study aims to assess the effect of agroecological intensification levels (lower (T1) and highest (T2)) on the soil C pool and aggregate stability and validate the correlation between different variables compared to the control (lowest/none (T3), where agroecological intensification was not applied. The C-stock, soil microbial biomass carbon (SMB-C), SOC, water extractable organic carbon (WEOC) in bulk soil, fine and coarse soil aggregates, and water-stable aggregates (WSA) were measured during maximum nutrient uptake in plants under diversified agroecological practices across different environmental conditions (core sites: Italy (CS1), France (CS2), Denmark (CS4), Spain (CS5), Netherlands (CS6), Lithuania (CS7), Turkey (CS8), and Belgium (CS9)). The soil aggregate stability varied among the CSs and treatments. At sites CS7 and CS9, WSA was higher in T1 and T2 compared to the control; a similar trend was observed at other sites, except CS1. SMB-C differed among the core sites, with the lowest value obtained in CS5 (52.3 μg g⁻¹) and the highest in CS6 (455.1 μg g⁻¹). The highest average contents of SOC and WEOC were obtained in bulk soil at CS2 (3.1 % and 0.3 g kg⁻¹ respectively). Positive and statistically significant (p < 0.001) correlations were detected among all variables tested with SOC in bulk soil and WSA. This study demonstrates the significance of agroecological practices in improving soil carbon stock and optimizing plant–soil–microbe interactions. Full article

It is important to ensure the ratio of stable and labile soil organic carbon (SOC) compounds in the soil as this influences ecosystem functions and the sustainability of soil management. The aim of this investigation was to determine the changes in SOC compounds and soil quality improvement in Arenosol soil after the conversion of arable land to natural and agricultural land use. The land use types included pine afforestation (PA), uncultivated abandoned land (UAL), unfertilised and fertilised cropland (CLunf, CLf), and unfertilised and fertilised grassland (GRunf, GRf). To assess the lability of organic carbon (OC) compounds, levels of mobile humic substances (MHSs), mobile humic acids (MHAs), mobile fulvic acids (MFAs), active C pool (POXC), and water-soluble C (WEOC) compounds were determined. It was found that faster OC accumulation occurs in PA soil than in CLf, and is somewhat slower in grassland uses (GRf and UAL). As the amount of SOC increased, more MHS formed. A significant increase in their quantity was found in PA (+92.2%) and CRf and UAL (+51.5–52.7%). The application of mineral fertilisers promoted the formation of MHSs in CLf and GRf. PA, GRunf, and GRf soils had more suitable conditions for MHA formation (MHA/MFA > 1.3), whereas CLunf soil contained more MFAs. The POXC pool was insensitive to land-use changes in the Arenosol. After land-use conversion, POXC amounts were significantly (p < 0.05) higher in natural ecosystems (UAL and PA) and fertiliser perennial grasses than in CL. The amount of WEOC increased the most in UAL, PA, and GRf (7.4–71.1%). The sequence of decrease in land use was GRf, UAL, and PA > CLunf, CLf, and GRunf. The decreasing order of the carbon management index (CMI) of different land uses (PA > UAL > GRf > GRunf > Clunf) confirms that faster OC accumulation in Arenosol soil occurred in PA and grassland land uses (GRf and UAL). The values of the carbon lability index (CLI) variation (CLunf > GRunf GRf > UAL > PA) show that in PA, UAL, and GRf land uses, mobile organic matter (OM) forms are relatively less formed, which stabilises OC accumulation in the soil. The CMI showed that UAL and GRf were the most suitable soil uses for Arenosol soils. Full article

The residual effect of compost and biochar amendment on soil properties and durum wheat response was evaluated under field conditions in a Mediterranean environment. The treatments compared in a randomized complete block experimental design with three replications were: mineral fertilizer (100 kg N ha⁻¹), compost applied at the rate of 25 Mg ha⁻¹, biochar applied at the rates of 10 and 30 Mg ha⁻¹, unfertilized control. Wheat was the second crop included in a sorghum–wheat cropping system and did not receive fertilizer supply. A hierarchical statistical analysis was carried out to investigate how different treatments could impact the cropping system performance. The findings highlight the significant influence of soil properties, particularly total N, WEOC, and TOC, on wheat and protein yield. One year after the amendment and fertilizer application, compost and biochar significantly increased soil total organic carbon content. The highest soil water extractable organic carbon was found with the compost application (76.9 mg kg⁻¹), whereas the lowest value (50 mg kg⁻¹) was with the highest rate of biochar. Soil respiration rates and hydraulic properties were not affected by the investigated treatments. This behavior is probably related to the short experimental duration and to the silty clayey soil texture. Significant correlations were observed between bulk density and water content at pressure heads in the −20 and −100 cm range; this range accounts for the effect of soil macro and mesopores. Multiple linear regression analysis revealed strong predictive power for grain (R²_{_adj} = 0.78; p < 0.001) and protein yield (R²_{_adj} = 0.77; p < 0.001). The highest grain yield (3.36 Mg ha⁻¹) was observed with compost, and the lowest (2.18 Mg ha⁻¹) with biochar at a rate of 30 Mg ha⁻¹. These findings lay the basis for understanding how different soil amendment management may impact soil quality and wheat performance, even in consideration of climate change. Full article

One of the practices often mentioned to achieve climate change mitigation is the long-term cultivation of perennial plants. The objective of the study was to estimate changes in the accumulation of soil organic carbon (SOC) and its fractions in 0–10, 10–20, 20–30 cm, and within 0–30 cm soil layer of red fescue (Festuca rubra L.) swards that differ in age (5, 10 and 15 years) as well as to compare them with the arable field. Our results show that SOC accumulation at 5-year-old cultivation of red fescue is high, later this SOC increase slowed down from 71% in the 0–30 cm soil layer when land use was converted from arable field to 5-year-old sward to 1% from 10 to 15 years. The level of water extractable organic carbon (WEOC) in the 0–30 cm soil layer of swards was significantly higher compared to the arable field. The positive effect of these swards in the accumulation and stabilization of organic carbon during humification in the soil was also determined. The largest amounts of mobile humic substances (MHS) and mobile humic acids (MHA) accumulated in the 0–10 cm layer of sward soil (3.30–4.93 and 1.53–2.48 g kg⁻¹, respectively). In conclusion, the findings suggest that a conversion from arable to soil under permanent grass cover significantly improves carbon status. Full article

Given the growth in the number of biogas power plants and the increase in the generation of waste from energy production, it is relevant to study the sustainable nature of this waste. Digestate is a product of the anaerobic digestion process, and is a valuable bio-fertilizer containing organic matter and nutrients necessary for agricultural plants’ growth. The study showed that different rates of liquid and solid phases of anaerobic digestate influenced the contents of carbon and nitrogen in genetically young soil in alluvial deposits—Fluvisol. The application of solid digestate (SD) considerably increased soil organic carbon content (SOC) in the 0–10 cm soil layer; however, SOC did not reach the 20–30 cm layer. Liquid digestate (LD) significantly increased SOC in the deeper layers. The levels of mineral nitrogen (N_min) and water extractable organic carbon (WEOC) increased in the 0–10 cm soil layer soon after fertilization with LD and SD. The mobile components of the soil (N_min and WEOC) were characterized by high variability during the growing season. Within the 2-month period, their concentrations decreased drastically and were close to those of unfertilized soil. The research indicates that anaerobic digestate had a greater effect on mobile forms of carbon and nitrogen in the soil than on their total amounts. Full article

Biogas slurry is widely used to fertilize crops. However, their impact on soil parameters and waxy winter wheat (Triticum aestivum L.) nutrition is poorly understood. The aim of this research was to determine the influence of liquid anaerobic digestate and pig slurry applied to waxy winter wheat on the dynamics of soil organic carbon (SOC) and total nitrogen (N_tot) in different forms on grain yield, and to compare them with the use of ammonium nitrate. The nitrogen rates (kg N·ha⁻¹) used for fertilization were N0, N60, N120, and N120+50. The study showed that the variation of nitrate nitrogen (N-NO₃) and water-extractable organic carbon (WEOC) in the soil during the growing season depended on N fertilizer rates, meteorological conditions of the year, and, to a lesser extent, on fertilizer forms. Meteorological conditions were responsible for the demand and supply of nutrients from the soil by the waxy winter wheat variety. This determined the wheat yield and the variation in the soil parameters studied. Over the 2 years, the soil C:N ratio decreased, especially at the medium and high N fertilizer rates. The lowest changes were observed in the unfertilized and fertilized plots at a rate of 60 kg N·ha⁻¹. Full article

In Mediterranean regions, the scarcity of freshwater for agricultural purposes is leading to the use of alternative water sources. This study aimed to evaluate the effects of long-term irrigation with reclaimed water on chemical and biological soil properties. On a mandarin tree orchard (Citrus clementina, cv. Orogrande), freshwater (FW) and tertiary reclaimed water (RW) were supplied for irrigation. In spring 2017, a soil sampling was carried out, collecting from each experimental plot four samples at 0–0.20 m depth. Chemical and biochemical soil properties were determined on air dried and sieved soil and on fresh and field-moist soil, respectively. The irrigation with reclaimed water significantly increased the soil water extractable organic carbon (WEOC), available P, Mg, and Na content, and the electrical conductivity (EC). Although not significant, the respiration rates and enzymatic activities were higher in RW treatment. The results of this research highlighted that the irrigation with reclaimed water, providing organic carbon and other nutrients, could have, in the long-term, beneficial effects on soil microorganism and their activities. In any case, especially in arid and semi-arid environments, a proper management of wastewater should be recommended to avoid soil degradation due to salt accumulation in the rootzone. Full article

Due to the increasing biomass of biowaste it is necessary to manage it rationally. This work presents comparisons and valorization of vermicomposts (VCs) and composts (Cs) prepared from various biowastes generated in households and private gardens, in terms of their practical use. The tested VCs and Cs were subjected to chemical analyses to assess the amounts of macro- (N, P, K, S, Mg, Ca, Na) and micronutrients (Fe, Zn, Mn, Cu, Ni), as well as contents of organic matter (OM), total organic carbon (TOC), humic compounds (HS) and labile and water extractable organic carbon (LC, WEOC). Moreover, humification indexes (HR, HI, DP) were determined. The amounts of macro- and micronutrients, OM, TOC, LC, WEOC were greater for vermicomposts. Regardless of these differences, both vermicomposts and composts were characterized by considerable amounts of organic matter ranging from 325 to 631 g·kg⁻¹ and TOC amounting from 82 to 270 g·kg⁻¹. Moreover, the tested organic fertilizers were characterized by high contents of N (7–21.5 g·kg⁻¹), K (3.7–24.4 g·kg⁻¹), Ca (12.2–44.0 g·kg⁻¹), Fe (133.1–333.8 mg·kg⁻¹) and Mn (71.5–113.8 mg·kg⁻¹). The analyzed VCs and Cs did not exceed the permissible amounts of heavy metals (Cr, Pb) and contained a comparable amount and quality of humus compounds. The level of C_HS ranged from 29.6 to 41 g·kg⁻¹ for vermicomposts, and from 19.8 to 51.8 g·kg⁻¹ for composts. The humification indexes indicate that VCs and Cs were well–matured despite different composting conditions. The HI values for VCs ranged from 8.3% to 10% and for Cs amounted from 12.2% to 16.8%. Similarly, the HR values were higher for composts (24.3–33%) in comparison to VCs (15.2–20.1%). Vermicomposting and composting of biowaste is economically and environmentally justified. Fertilizers obtained in the composting process are a valuable source of organic material and nutrients essential for plants and can be safely used in private gardens. Full article

Soil-dissolved organic matter (DOM) drives the carbon (C) and nitrogen (N) cycles in agroecosystems. Despite many studies on DOM dynamics, hardly any attention has been directed toward DOM quality, particularly DOM composition. The aim of this study was to elucidate how C and N management practices alter soil water-extractable organic matter (WEOM) in a loess soil agroecosystem. Field experiments were conducted with a winter wheat monoculture. Three N fertilization rates (0, 120, and 240 kg ha⁻¹ year⁻¹) were applied for 17 years (2002–2019), combined with five C practices (zero, low, and high rates of sheep manure or wheat straw) for three years (2016–2019). The results reveal that soil organic carbon (SOC) and water-extractable organic carbon (WEOC) concentrations in the topsoil (0–20 cm) were increased by organic amendments considerably but were not affected by N fertilization. The fluorescence excitation–emission matrix spectra (EEM) of WEOM were resolved to two humic-like components (C1 and C2) and two soluble microbial byproduct-like components (C3 and C4). The proportions of C1 and C2 were increased, while the proportion of C3 was decreased by both C and N management practices. In conclusion, organic amendments increased both WEOM quality and its proportion of humic-like components, whereas N fertilization increased the proportion of humic-like components without variations of WEOM quality in the topsoil of loess soil. Full article

Biochar amendments are widely recognized to improve crop productivity and soil biogeochemical quality, however, their effects on vegetable crops are less studied. This pot study investigated the effects of cotton stick, corncob and rice straw biochars alone and with farmyard manure (FYM) on tomato growth, soil physico–chemical and biological characteristics, soil organic carbon (SOC) content and amount of soil nutrients under recommended mineral fertilizer conditions in a nutrient-depleted alkaline soil. Biochars were applied at 0, 1.5 and 3% (w/w, basis) rates and FYM was added at 0 and 30 t ha⁻¹ rates. Biochars were developed at 450 °C pyrolysis temperature and varied in total organic C, nitrogen (N), phosphorus (P) and potassium (K) contents. The results showed that biochars, their amounts and FYM significantly improved tomato growth which varied strongly among the biochar types, amounts and FYM. With FYM, the addition of 3% corncob biochar resulted in the highest total chlorophyll contents (9.55 ug g⁻¹), shoot (76.1 cm) and root lengths (44.7 cm), and biomass production. Biochars with and without FYM significantly increased soil pH, electrical conductivity (EC) and cation exchange capacity (CEC). The soil basal respiration increased with biochar for all biochars but not consistently after FYM addition. The water-extractable organic C (WEOC) and soil organic C (SOC) contents increased significantly with biochar amount and FYM, with the highest SOC found in the soil that received 3% corncob biochar with FYM. Microbial biomass C (MBC), N (MBN) and P (MBP) were the highest in corncob biochar treated soils followed by cotton stick and rice straw biochars. The addition of 3% biochars along with FYM also showed significant positive effects on soil mineral N, P and K contents. The addition of 3% corncob biochar with and without FYM always resulted in higher soil N, P and K contents at the 3% rate. The results further revealed that the positive effects of biochars on above-ground plant responses were primarily due to the improvements in below-ground soil properties, nutrients’ availability and SOC; however, these effects varied strongly between biochar types. Our study concludes that various biochars can enhance tomato production, soil biochemical quality and SOC in nutrient poor soil under greenhouse conditions. However, we emphasize that these findings need further investigations using long-term studies before adopting biochar for sustainable vegetable production systems. Full article

Both altitude and vegetation are known to affect the amount and quality of soil organic matter (SOM) and the size and activity of soil microbial biomass. However, when altitude and vegetation changes are combined, it is still unclear which one has a greater effect on soil chemical and biochemical properties. With the aim of clarifying this, we tested the effect of altitude (and hence temperature) and vegetation (broadleaf vs pine forests) on soil organic carbon (SOC) and soil microbial biomass and its activity. Soil sampling was carried out in two adjacent toposequences ranging from 500 to 1000 m a.s.l. on a calcareous massif in central Italy: one covered only by Pinus nigra J.F. Arnold forests, while the other covered by Quercus pubescens Willd., Ostrya carpinifolia Scop. and Fagus sylvatica L. forests, at 500, 700 and 1000 m a.s.l., respectively. The content of SOC and water-extractable organic carbon (WEOC) increased with altitude for the pine forests, while for the broadleaf forests no trend along the slope occurred, and the highest SOC and WEOC contents were observed in the soil at 700 m under the Ostrya carpinifolia forest. With regard to the soil microbial community, although the size of the soil microbial biomass (Cmic) generally followed the SOC contents along the slope, both broadleaf and pine forest soils showed similar diminishing trends with altitude of soil respiration (ΣCO2-C), and ΣCO2-C:WEOC and ΣCO2-C:Cmic ratios. The results pointed out that, although under the pine forests’ altitude was effective in affecting WEOC and SOC contents, in the soils along the broadleaf forest toposequence this effect was absent, indicating a greater impact of vegetation than temperature on SOC amount and pool distribution. Conversely, the similar trend with altitude of the microbial activity indexes would indicate temperature to be crucial for the activity of the soil microbial community. Full article

Processes controlling microbial access to soil organic matter are critical for soil nutrient cycling and C stabilization. The bioavailability of soil organic matter partly depends on the rate that substrates become water-soluble, which is determined by some combination of biological, biochemical, and purely abiotic processes. Our goal was to unravel these biotic and abiotic processes to better understand mechanisms controlling the dynamics of bioavailable soil organic carbon (SOC). We sampled soils in a California annual grassland from manipulated plots with and without plants to help distinguish bioavailable SOC generated from mineral-associated organic matter versus from plant detritus (i.e., the “light fraction”). In the laboratory, soils were incubated for 8 months under all possible combinations of three levels of moisture and two levels of microbial biomass using continuous chloroform sterilization. We measured cumulative carbon dioxide (CO₂) production and the net change in soil water-extractable organic C (WEOC) to quantify C that was accessed biologically or biochemically. Under the driest conditions, microbes appeared to primarily access WEOC from recent plant C, with the other half of CO₂ production explained by extracellular processes. These results suggest that dry, uncolonized conditions promote the adsorption of WEOC onto mineral surfaces. Under wetter conditions, microbial access increased by two orders of magnitude, with a large concomitant decrease in WEOC, particularly in soils without plant inputs from the previous growing season. The largest increase in WEOC occurred in wet sterilized soil, perhaps because exoenzymes and desorption continued solubilizing C but without microbial consumption. A similar amount of WEOC accumulated in wet sterilized soil whether plants were present or not, suggesting that desorption of mineral-associated C was the abiotic WEOC source. Based on these results, we hypothesize that dry-live and wet-uncolonized soil microsites are sources of bioavailable SOC, whereas wet-live and dry-uncolonized microsites are sinks. Full article